CN114927674B - Lithium cobalt oxide positive electrode material, preparation method and application thereof - Google Patents

Lithium cobalt oxide positive electrode material, preparation method and application thereof Download PDF

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CN114927674B
CN114927674B CN202210721830.8A CN202210721830A CN114927674B CN 114927674 B CN114927674 B CN 114927674B CN 202210721830 A CN202210721830 A CN 202210721830A CN 114927674 B CN114927674 B CN 114927674B
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oxide
lithium
cobalt oxide
lithium cobalt
positive electrode
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CN114927674A (en
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朱二涛
赵亚楠
李刚
陆胡彪
张媛
胡刚刚
吴胜坤
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Hefei Rongjie Energy Materials Co ltd
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Abstract

The invention discloses a lithium cobalt oxide positive electrode material, a preparation method and application thereof, wherein the preparation method of the lithium cobalt oxide positive electrode material mainly comprises the following steps: providing cobaltosic oxide a having a median particle size d50=12-17 μm and cobaltosic oxide B having a median particle size d50=3-7 μm; preparing single-crystal lithium cobalt oxide and single-crystal-like lithium cobalt oxide; providing a conductive oxide, wherein the conductive oxide is fluorine doped tin oxide; the monocrystal-like lithium cobaltate and the monocrystal-like lithium cobaltate are mixed according to the mass ratio of 1-9:1-5, mixing to obtain a lithium cobaltate mixed material; and fully mixing the lithium cobalt oxide mixture and the conductive oxide, and sintering to obtain the coated modified lithium cobalt oxide anode material. The lithium cobaltate anode material has the advantages of high multiplying power, high compaction and high voltage, and simultaneously has excellent high-temperature cycle performance.

Description

Lithium cobalt oxide positive electrode material, preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium secondary batteries, and particularly relates to a preparation method of a lithium cobalt oxide positive electrode material, a lithium cobalt oxide positive electrode material prepared by the preparation method, and application of the lithium cobalt oxide positive electrode material serving as a positive electrode active substance in preparation of a lithium ion battery.
Background
LiCoO 2 The positive electrode material has the advantages of high energy density, high working voltage, high tap density, high safety, long cycle life and the like, and is one of key materials with the widest application range and the most prospect in the field of lithium ion batteries. With the development of electronic products, the battery energy is improvedThe requirement of the volume density is higher, and for lithium cobaltate, the specific capacity of the lithium cobaltate material can be improved by increasing the charge cut-off voltage of the lithium cobaltate material, but the cycle and rate performance of the lithium cobaltate are reduced, so that the lithium cobaltate material needs to be subjected to coating modification.
At present, the materials used for industrially producing the surface coating of the anode active material at home and abroad are mainly metal oxide powder, and the purpose of surface coating is achieved by mixing and sintering the coating materials and the anode active material, but the ionic conductivity of the coating layer is lower, and the intercalation and release of lithium ions can be inhibited in the subsequent electrochemical reaction process, so that the capacity and the multiplying power performance of the material are reduced. And the lithium cobalt oxide anode materials have the problems of poor rate performance and poor high-temperature cycle performance.
Disclosure of Invention
In view of the above, the present invention is to provide a method for preparing a lithium cobalt oxide positive electrode material, which comprises the steps of grading and blending two kinds of lithium cobalt oxides with different morphologies, namely large-particle single-crystal lithium cobalt oxide and small-particle single-crystal lithium cobalt oxide; and the lithium cobalt oxide anode material is coated by adopting conductive oxide after being mixed, so that the electrical property of the lithium cobalt oxide anode material is improved, the corrosion of electrolyte to a matrix material is well isolated, the structural stability of lithium cobalt oxide is improved, and the prepared lithium cobalt oxide anode material has the advantages of high multiplying power, high compaction and high voltage and has excellent high-temperature cycle performance.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the invention provides a preparation method of a lithium cobalt oxide positive electrode material, which comprises the following steps:
providing cobaltosic oxide a having a median particle size d50=12-17 μm and cobaltosic oxide B having a median particle size d50=3-7 μm;
preparing single-crystal lithium cobalt oxide and single-crystal-like lithium cobalt oxide: taking the cobaltosic oxide A and the cobaltosic oxide B, and respectively mixing with Li 2 CO 3 Mixing with additives, and calcining to obtain monocrystalline lithium cobalt oxide and monocrystalline-like lithium cobalt oxide;
providing a conductive oxide, wherein the conductive oxide is fluorine doped tin oxide;
coating lithium cobaltate: the monocrystal-like lithium cobaltate and the monocrystal-like lithium cobaltate are mixed according to the mass ratio of 1-9:1-5, mixing to obtain a lithium cobaltate mixed material; and fully mixing the lithium cobalt oxide mixture and the conductive oxide, and sintering to obtain the coated modified lithium cobalt oxide anode material.
Further, the cobaltosic oxide A or the cobaltosic oxide B are respectively mixed with Li 2 CO 3 Mixing materials according to the molar ratio of lithium to cobalt of 1.03-1.07.
Further, the additive is Mg (OH) 2 、Al 2 O 3 、Y 2 O 3 And Co (OH) 2 ；
Preferably, the Mg (OH) is based on the mass of the tricobalt tetraoxide A or tricobalt tetraoxide B 2 The addition amount of (2) is 0.7% -1%, al 2 O 3 The addition amount of (C) is 0.8-1.5%, Y 2 O 3 The addition amount of the catalyst is 0.2% -0.5%, and the Co (OH) 2 The addition amount of (2) is 1.8% -3%.
Further, the speed of the mixed material is 500-800rpm, and the time is 20-40min.
According to a further scheme, the preparation of the monocrystal-like lithium cobaltate adopts gradient calcination, and the gradient calcination process is specifically that the sintering is performed for 6-8 hours at 900-920 ℃ and then the temperature is raised to 960-990 ℃ and the temperature is kept for 4-6 hours.
Further, the conductive oxide is prepared by a sol-gel method, and comprises the following steps:
adding the first metal salt into a solvent to dissolve completely, adding the second metal salt, stirring at a constant temperature of 50-70 ℃ to dissolve the first metal salt sufficiently to obtain a clear and transparent sol-like solution, aging at room temperature, standing to gel, drying and grinding into powder for later use;
preferably, the solvent is in a volume ratio of 1:15-30 of water and ethanol;
preferably, the first metal salt is selected from stannous chloride pentahydrate and the second metal salt is selected from SnF 2 ；
Preferably, the molar ratio of the first metal salt to the second metal salt is 2-20:1.
further, the conductive oxide accounts for 1-5wt% of the total mass of the lithium cobaltate.
Further, the sintering process is that sintering is carried out in an air kiln for 8-12h at 700-950 ℃.
The invention further discloses a lithium cobalt oxide anode material which is prepared by the preparation method.
The invention further discloses a lithium ion battery, which comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the active material of the positive electrode contains the lithium cobaltate positive electrode material.
Compared with the prior art, the invention has the following beneficial effects:
the invention uses the traditional two-stage method to sinter and synthesize lithium cobaltate, the raw material adopts two kinds of cobaltic oxides with different granularity sizes to prepare monocrystal type and monocrystal-like lithium cobaltate respectively, and the material is subjected to solid phase synthesis coating modification by selecting specific conductive oxides after mixing, sintering and crushing according to a certain proportion.
The monocrystal-like lithium cobalt oxide has good multiplying power performance, good monocrystal-like lithium cobalt oxide capacity, good circulation performance and high compaction density, and the monocrystal-like small-particle lithium cobalt oxide and monocrystal-like large-particle lithium cobalt oxide are graded, so that the processing performance of the lithium cobalt oxide positive electrode material can be improved, and the compaction density and the energy density of the lithium cobalt oxide positive electrode material are improved, so that the high-multiplying power, high-compaction, high-capacity and high-voltage lithium cobalt oxide positive electrode material is prepared. The used conductive oxide not only can play a role of a coating layer, but also can improve the electronic conductivity of the surface of the lithium cobalt oxide particles and improve the rate capability and high-temperature cycle performance of the lithium cobalt oxide anode material due to the excellent conductive performance; and the chemical stability is good, and side reaction with electrolyte is not easy to occur.
Drawings
FIG. 1 is a scanning electron microscope image of a lithium cobaltate cathode material prepared in example 2 of the present invention;
FIG. 2 is a graph showing the high temperature cycle performance of example 2 and comparative example 3 of the present invention.
Detailed Description
The following detailed description of embodiments of the invention is exemplary and is provided merely to illustrate the invention and is not to be construed as limiting the invention.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The first aspect of the invention provides a preparation method of a lithium cobalt oxide positive electrode material, which comprises the following steps:
preparation of monocrystalline lithium cobalt oxide and monocrystalline-like lithium cobalt oxide
Specifically, tricobalt tetraoxide A having a median particle diameter D50=12 to 17 μm is taken and mixed with Li 2 CO 3 And mixing the additives and calcining to obtain the single-crystal lithium cobalt oxide. Wherein, tricobalt tetraoxide A and Li 2 CO 3 Can be mixed in the proportions conventional in the art, according to embodiments of the invention, tricobalt tetraoxide A and Li 2 CO 3 Mixing according to the molar ratio of lithium to cobalt of 1.03-1.07, wherein mixing parameters are not particularly limited, and the mixing speed is 500-800rpm and the time is 20-40min according to the embodiment of the invention based on uniform mixing and no white spots.
Further, the additive herein is Mg (OH) 2 、Al 2 O 3 、Y 2 O 3 And Co (OH) 2 Wherein Mg (OH) 2 The electronic conductivity of the material can be improved; al (Al) 2 O 3 The crystal structure can be stabilized, and the material cycle performance is improved; y is Y 2 O 3 The addition of the catalyst can expand the unit cell parameters a and c axes of the material, which is favorable for better deintercalation and intercalation of lithium ions, thereby improving the specific capacity of the material and improving the high-temperature cycle performance of the material; co (OH) 2 The effect of eliminating the residual alkali on the surface can be achieved. By a plurality of additivesThe introduction of (3) imparts excellent properties to the lithium cobaltate cathode material. According to an embodiment of the present invention, the Mg (OH) is calculated on the basis of the mass of the tricobalt tetraoxide a 2 The addition amount of (2) is 0.7% -1%, al 2 O 3 The addition amount of (C) is 0.8-1.5%, Y 2 O 3 The addition amount of the catalyst is 0.2% -0.5%, and the Co (OH) 2 The addition amount of (2) is 1.8% -3%.
Further, in the preparation of the single-crystal type lithium cobaltate, the calcination temperature is 1000-1100 ℃ for 8-14 hours, preferably 1050 ℃ for 12 hours.
Specifically, tricobalt tetraoxide B having a median particle diameter D50=3-7 μm is taken and mixed with Li 2 CO 3 And mixing the additives and calcining to obtain the monocrystal-like lithium cobalt oxide. The preparation of the monocrystal-like lithium cobalt oxide is similar to that of the monocrystal-like lithium cobalt oxide, and the main difference is that in the preparation process of the monocrystal-like lithium cobalt oxide, gradient sintering is adopted for calcination, and a specific gradient sintering process is that the temperature is kept for 6-8 hours before 900-920 ℃, and then the temperature is raised to 960-990 ℃ and kept for 4-6 hours; preferably, the pre-sintering is performed at 900 ℃ for 6 hours, and then the temperature is increased to 970 ℃ for 4 hours. Other choices, proportions, and addition of additives, such as cobalt source and lithium source, are the same as those of the preparation of single crystal lithium cobaltate, and thus are not specifically described herein.
Preparation of conductive oxides
The conductive oxide is fluorine doped tin oxide, and the material has low resistivity, high conductivity and ion conductivity by coating the fluorine doped tin oxide on the surface of the material, so that the rate performance and high-temperature cycle performance of the material are further improved. In particular, fluorine doped tin oxide has good electrochemical performance, and the advantages of good chemical stability, no toxicity and low resistivity can improve the rate capability and high temperature cycle performance of the lithium cobaltate material.
Further, according to an embodiment of the present invention, the preparation of the conductive oxide fluorine doped tin oxide is prepared by a sol-gel method known in the art, and the specific steps are as follows:
adding the first metal salt into the solvent for complete dissolutionAdding a second metal salt, stirring at 50-70deg.C to dissolve thoroughly to obtain clear transparent sol solution, aging at room temperature, standing to gel, drying, and grinding into powder to obtain nanometer fluoride particles. Wherein the volume ratio of the solvent is 1:15-30 of water and ethanol; the first metal salt is selected from stannous chloride pentahydrate, and the second metal salt is selected from SnF 2 The method comprises the steps of carrying out a first treatment on the surface of the The molar ratio of the first metal salt to the second metal salt is 2-20:1.
coating lithium cobalt oxide
Specifically, the monocrystalline-like lithium cobaltate and the monocrystalline-like lithium cobaltate are mixed according to the mass ratio of 1-9:1-5, mixing to obtain a lithium cobaltate mixed material; and then fully mixing the lithium cobalt oxide mixture and the conductive oxide, and sintering to obtain the coated modified lithium cobalt oxide positive electrode material.
The processing performance of the material can be improved by mixing large-particle monocrystalline lithium cobalt oxide and small-particle monocrystalline lithium cobalt oxide, so that the compaction density and the energy density of the material are improved. And then, conducting oxide and lithium cobaltate are subjected to solid phase mixed sintering, so that the finally prepared lithium cobaltate anode material has high multiplying power, high capacity and high voltage and also has good cycle performance at high temperature. In addition, the adoption of the solid phase coating has the advantages of simple and convenient preparation process, stable performance, high specific capacity and good cycle performance.
Further, it can be appreciated that the degree of coating of the conductive oxide on the surface of the lithium cobaltate can be adjusted by adjusting the amount of the conductive oxide, which in turn adjusts the performance of the lithium cobaltate cathode material. According to an embodiment of the invention, the conductive oxide comprises 1-5wt% of the total mass of lithium cobaltate.
Further, the sintering process after mixing can be adjusted according to practical situations, and according to the embodiment of the invention, the sintering process is that sintering is carried out for 8-12 hours at 700-950 ℃ in an air kiln.
In a second aspect, the invention provides a lithium cobalt oxide positive electrode material prepared by the preparation method according to the first aspect of the invention.
In a third aspect, the invention provides a lithium ion battery, which comprises a positive electrode, a negative electrode, a separator and electrolyte, wherein the active material of the positive electrode contains the lithium cobaltate positive electrode material according to the second aspect of the invention.
The present invention will be illustrated by the following examples, which are given for illustrative purposes only and are not intended to limit the scope of the present invention in any way, and unless otherwise specified, the conditions or procedures not specifically described are conventional and the reagents and materials employed are commercially available.
Example 1
Preparation of large-particle single-crystal lithium cobaltate material
The cobalt tetraoxide (Co) was taken at a molar ratio of 1.07 3 O 4 ) And technical grade lithium carbonate (Li) 2 CO 3 ) The method comprises the steps of carrying out a first treatment on the surface of the Taking 0.7% of Mg (OH) by mass of cobaltosic oxide 2 、0.8％Al 2 O 3 And 0.5% Y 2 O 3 2% Co (OH) 2 . Will be configured with Co 3 O 4 、Li 2 CO 3 、Mg(OH) 2 、Al 2 O 3 、Y 2 O 3 And Co (OH) 2 Sequentially adding the materials into a high-speed mixer, mixing at 600rpm for 30min, uniformly mixing for no white point, calcining the mixture at 1050 ℃ for 12h in an air kiln, cooling to room temperature along with the furnace, and performing jet milling to obtain a pre-product; wherein, the cobaltosic oxide adopted is spherical aluminum-doped Co 3 O 4 Median particle size d50=12.5 μm.
Preparation of small-particle monocrystalline lithium cobaltate material
Tricobalt tetraoxide (Co) was taken at a molar ratio of lithium to cobalt of 1.05 3 O 4 ) And technical grade lithium carbonate (Li) 2 CO 3 ) The method comprises the steps of carrying out a first treatment on the surface of the Taking 0.7% of Mg (OH) by mass of cobaltosic oxide 2 、0.8％Al 2 O 3 And 0.5% Y 2 O 3 2% Co (OH) 2 The method comprises the steps of carrying out a first treatment on the surface of the Will be configured with Co 3 O 4 、Li 2 CO 3 、Mg(OH) 2 、Al 2 O 3 、Y 2 O 3 And Co (OH) 2 Sequentially adding the materials into a high-speed mixer, mixing at 600rpm for 30min, uniformly mixing for no white spots, performing gradient sintering on the mixture in an air kiln, heating to 900 ℃ for calcination for 6 hours, heating to 960 ℃ for calcination for 4 hours, cooling to room temperature along with a furnace, and performing jet milling to obtain a pre-product; wherein, the cobaltosic oxide is ball-like aluminum-doped Co 3 O 4 Median particle size d50=4.5 μm.
Preparation of coated conductive oxide powders
Stannous chloride pentahydrate (SnCl) 2 ·5H 2 O) is dissolved in ethanol and deionized water, and after the solution is fully dissolved, the solution is prepared according to n (SnF) 2 )：n(SnCl 4 ·5H 2 O) =11 mol%, i.e. F/sn=22 mol%, by doping fluorine, snF 2 Adding into the above solution, selecting ethanolamine (NH) 2 CH 2 CH 2 OH) is used as a dispersing agent, a dispersing agent with mass such as stannous chloride pentahydrate is added into the solution after stirring, the solution is stirred in a water bath at 60 ℃ until the dispersing agent is fully dissolved, a clear and transparent solution is obtained, the solution is cooled and then stands for 24 hours at room temperature, sol liquid of the prepared FTO film is put into a blast drying oven for drying at 150 ℃ for 1.5 hours, and the powder is ground for standby.
Preparation of lithium cobalt oxide positive electrode material
The mixing mass ratio is that single crystal lithium cobaltate: mixing the monocrystal-like lithium cobaltate=7:3 to obtain mixed lithium cobaltate powder, adding the prepared conductive oxide into the mixed lithium cobaltate powder, mixing the mixture for 30min in a high mixer, sintering the mixture in an air kiln at 910 ℃ for 10h after the mixing is finished to obtain the coated modified lithium cobaltate positive electrode material.
Example 2
Preparation of large-particle single-crystal lithium cobaltate material
Taking cobaltosic oxide (Co) according to the molar ratio of lithium to cobalt of 1.065 3 O 4 ) And technical grade lithium carbonate (Li) 2 CO 3 ) The method comprises the steps of carrying out a first treatment on the surface of the With tricobalt tetraoxide1% Mg (OH) by mass 2 、1％Al 2 O 3 、0.5％Y 2 O 3 And 1.8% Co (OH) 2 The method comprises the steps of carrying out a first treatment on the surface of the Will be configured with Co 3 O 4 、Li 2 CO 3 、Mg(OH) 2 、Al 2 O 3 、Y 2 O 3 And Co (OH) 2 Sequentially adding the materials into a high-speed mixer, mixing at 600rpm for 30min, uniformly mixing for no white point, calcining the mixture at 1050 ℃ for 12h in an air kiln, cooling to room temperature along with the furnace, and performing jet milling to obtain a pre-product. The cobaltosic oxide spherical aluminum-doped Co 3 O 4 Median particle size d50=12.5 μm.
Preparation of small-particle monocrystalline lithium cobaltate material
The tricobalt tetraoxide (Co) is taken according to the molar ratio of lithium to cobalt of 1.055 3 O 4 ) And technical grade lithium carbonate (Li) 2 CO 3 ) The method comprises the steps of carrying out a first treatment on the surface of the Taking 1% of Mg (OH) by mass of cobaltosic oxide 2 、1％Al 2 O 3 And 0.5% Y 2 O 3 And 1.8% Co (OH) 2 The method comprises the steps of carrying out a first treatment on the surface of the Will be configured with Co 3 O 4 、Li 2 CO 3 、Mg(OH) 2 、Al 2 O 3 、Y 2 O 3 And Co (OH) 2 Sequentially adding the materials into a high-speed mixer, mixing at 600rpm for 30min, uniformly mixing for no white spots, performing gradient sintering on the mixture in an air kiln, heating to 900 ℃ for calcination for 6h, heating to 960 for calcination for 4h, cooling to room temperature along with a furnace, and performing jet milling to obtain a pre-product. The cobaltosic oxide ball-shaped aluminum-doped Co 3 O 4 Median particle size d50=4.5 μm.
Preparation of coated conductive oxide powders
An amount of stannous chloride pentahydrate (SnCl) 2 ·5H 2 O) is dissolved in ethanol and deionized water, and after the solution is fully dissolved, the solution is prepared according to n (SnF) 2 )：n(SnCl 4 ·5H 2 O) =1 mol%, i.e. F/sn=22 mol%, by doping fluorine, snF 2 Adding into the above solution, selecting ethanolamine (NH) 2 CH 2 CH 2 OH) is used as a dispersing agent, a dispersing agent with mass such as stannous chloride pentahydrate is added into the solution after stirring, the solution is stirred in a water bath at 60 ℃ until the dispersing agent is fully dissolved, a clear and transparent solution is obtained, the solution is cooled and then stands for 24 hours at room temperature, sol liquid of the prepared FTO film is put into a blast drying oven for drying at 150 ℃ for 1.5 hours, and the powder is ground for standby.
Preparation of lithium cobalt oxide positive electrode material
The mixing proportion is that single crystal lithium cobalt oxide: and agglomerating lithium cobaltate=8:2 to obtain blended lithium cobaltate powder, adding the prepared conductive oxide into the blended lithium cobaltate powder, mixing in a high mixer for 30min, sintering the conductive oxide/lithium cobaltate=3.5 wt% in an air kiln for 10h at 910 ℃ after mixing, and obtaining the coated modified lithium cobaltate positive electrode material.
The microscopic characterization of the lithium cobalt oxide cathode material in this example is shown in fig. 1, and it can be seen from fig. 1 that the surface of the lithium cobalt oxide cathode material is smooth and the coating is very uniform.
Example 3
Preparation of large-particle single-crystal lithium cobaltate material
Taking cobaltosic oxide (Co) according to the molar ratio of lithium to cobalt of 1.06 3 O 4 ) And technical grade lithium carbonate (Li) 2 CO 3 ) The method comprises the steps of carrying out a first treatment on the surface of the Taking 1% of Mg (OH) by mass of cobaltosic oxide 2 、1.5％Al 2 O 3 、0.5％Y 2 O 3 And 3% Co (OH) 2 The method comprises the steps of carrying out a first treatment on the surface of the Will be configured with Co 3 O 4 、Li 2 CO 3 、Mg(OH) 2 、Al 2 O 3 、Y 2 O 3 And Co (OH) 2 Sequentially adding the materials into a high-speed mixer, mixing at 600rpm for 30min, uniformly mixing for no white point, calcining the mixture at 1050 ℃ for 12h in an air kiln, cooling to room temperature along with the furnace, and performing jet milling to obtain a pre-product. The spherical aluminum-doped Co 3 O 4 Median particle size d50=12.5 μm.
Preparation of small-particle monocrystalline lithium cobaltate material
According to mole of lithium cobaltThe ratio of cobalt oxide to cobalt (Co) 3 O 4 ) And technical grade lithium carbonate (Li) 2 CO 3 ) The method comprises the steps of carrying out a first treatment on the surface of the Taking 1% of Mg (OH) by mass of cobaltosic oxide 2 、1.5％Al 2 O 3 、0.5％Y 2 O 3 And 3% Co (OH) 2 The method comprises the steps of carrying out a first treatment on the surface of the Will be configured with Co 3 O 4 、Li 2 CO 3 、Mg(OH) 2 、Al 2 O 3 、Y 2 O 3 And Co (OH) 2 Sequentially adding the materials into a high-speed mixer, mixing at 600rpm for 30min, uniformly mixing for no white spots, performing gradient sintering on the mixture in an air kiln, heating to 900 ℃ for calcination for 6h, heating to 960 for calcination for 4h, cooling to room temperature along with a furnace, and performing jet milling to obtain a pre-product. The spheroidal aluminum-doped Co 3 O 4 Median particle size d50=4.5 μm.
Preparation of coated conductive oxide powders
An amount of stannous chloride pentahydrate (SnCl) 2 ·5H 2 O) is dissolved in ethanol and deionized water, and after the solution is fully dissolved, the solution is prepared according to n (SnF) 2 ):n(SnCl 4 ·5H 2 O) =11 mol%, i.e. F/sn=22 mol%, and SnF 2 Adding into the above solution, selecting ethanolamine (NH) 2 CH 2 CH 2 OH) is used as a dispersing agent, a dispersing agent with mass such as stannous chloride pentahydrate is added into the solution after stirring, the solution is stirred in a water bath at 60 ℃ until the dispersing agent is fully dissolved, a clear and transparent solution is obtained, the solution is cooled and then stands for 24 hours at room temperature, sol liquid of the prepared FTO film is put into a blast drying oven for drying at 150 ℃ for 1.5 hours, and the powder is ground for standby.
Preparation of lithium cobalt oxide positive electrode material
The mixing proportion is that single crystal lithium cobalt oxide: and agglomerating lithium cobaltate=6:4 to obtain blended lithium cobaltate powder, adding the prepared conductive oxide into the blended lithium cobaltate powder, mixing in a high mixer for 30min, sintering the conductive oxide/lithium cobaltate=4 wt% in an air kiln for 10h at 910 ℃ after mixing, and obtaining the coated modified lithium cobaltate positive electrode material.
Comparative example 1
Preparation of large-particle single-crystal lithium cobaltate material
As in example 2.
The large-particle single-crystal lithium cobaltate material was coated with the conductive oxide in the same manner as in example 2 to prepare a lithium cobaltate positive electrode material.
Comparative example 2
Preparation of small-particle monocrystalline lithium cobaltate material
As in example 2.
The single-crystal type small-particle lithium cobaltate material is coated with conductive oxide in the same manner as in example 2, and then the lithium cobaltate positive electrode material is prepared.
Comparative example 3
The large-particle single-crystal type lithium cobalt oxide material in comparative example 1 and the small-particle single-crystal type lithium cobalt oxide material in comparative example 2 are directly subjected to coating according to the mass ratio of 8:2, carrying out electrical property test after mixing uniformly.
Comparative example 4
The present comparative example uses the same embodiment as in example 2, except that: y is not added in the preparation of large-particle single-crystal lithium cobalt oxide material and small-particle single-crystal lithium cobalt oxide material 2 O 3 The additive was the same as in example 2 except that a lithium cobaltate positive electrode material was prepared.
Test case
The modified lithium cobaltates of examples and comparative examples were assembled as positive electrode materials into full cells, and the above-described modified LiCoO was prepared 2 Mixing with conductive agent Super P and binder polyvinylidene fluoride (PVDF) according to a mass ratio of 96:2:2 dispersing in a Nitrogen Methyl Pyrrolidone (NMP) solvent, uniformly stirring to obtain electrode slurry, coating the electrode slurry on the surface of an aluminum foil, baking for 12 hours at 120 ℃ in vacuum, rolling, and cutting to obtain an anode electrode plate; with graphite cathode, 1mol/L LiPF is used 6 And (C+DEC+DMC) electrolyte (volume ratio is 1:1:1), and the PP/PE/PP three-layer diaphragm is made into the soft package battery. The charge and discharge tests were carried out at 25℃and 45℃and 4.4V/0.2℃respectively. The results are shown in table 1 and fig. 2.
TABLE 1 full cell Performance test at 25℃in examples 1-3, comparative examples 1-4
As can be seen from Table 1, the lithium cobaltate sample prepared in example 1 was used as a positive electrode active material, and the compacted density of the electrode sheet was measured and found to be 4.01g/cm 3 Graphite is used as a negative electrode to assemble a soft package battery and the battery performance tester is used for testing the electrical performance of the battery. The charge-discharge cut-off voltage is 3.0-4.4V, the charging multiplying power is 0.2C, the measured specific capacity of the first 1C discharge is 174.24mAh/g, and the discharge capacities of different discharge multiplying powers of 2C, 5C, 10C, 15C and 20C respectively reach 99.57%, 97.46%, 95.59%, 94.25% and 86.25% of the discharge capacity of 1C. As shown in FIG. 2, the battery capacity retention rate was 81% at a cycle of 350 weeks by performing 1C/1C charge/discharge at 45℃and a voltage interval of 3.0 to 4.4V.
Compared with example 1, the lithium cobaltate in comparative example 3 is not coated by conductive fluoride, so that the cycle retention rate is lower and the rate capability is lower; comparative example 1 and comparative example 2 were not subjected to size grading, resulting in lower discharge specific capacity and lower compaction of the materials, compared to example 1. The production process uses the steps of grading the large and small particles and then coating the particles, so that the solid phase coating is carried out on the material, the production process is simplified, the cost is saved, and the uniformity of the distribution of the coating material in the coating layer is relatively good.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims (7)

1. The preparation method of the lithium cobalt oxide positive electrode material is characterized by comprising the following steps of:
providing cobaltosic oxide a having a median particle size d50=12-17 μm and cobaltosic oxide B having a median particle size d50=3-7 μm;
preparing single-crystal lithium cobalt oxide and single-crystal-like lithium cobalt oxide: taking the cobaltosic oxide A and the cobaltosic oxide B, and respectively mixing with Li 2 CO 3 Mixing with additive and calcining to obtain monocrystal lithium cobaltate and monocrystal-like lithium cobaltate, wherein the cobaltosic oxide A or the cobaltosic oxide B are respectively mixed with Li 2 CO 3 Mixing materials according to the molar ratio of lithium to cobalt of 1.03-1.07, wherein the additive is Mg (OH) 2 、Al 2 O 3 、Y 2 O 3 And Co (OH) 2 ；
Providing a conductive oxide, wherein the conductive oxide is fluorine doped tin oxide;
coating lithium cobaltate: the monocrystal type lithium cobalt oxide and the monocrystal-like lithium cobalt oxide are mixed according to the mass ratio of 1-9:1-5, mixing to obtain a lithium cobaltate mixed material; fully mixing the lithium cobalt oxide mixture and the conductive oxide, and sintering to obtain a coated modified lithium cobalt oxide anode material;
wherein the conductive oxide accounts for 1-5wt% of the total mass of the lithium cobaltate, and the conductive oxide is prepared by a sol-gel method, and comprises the following steps:
SnCl is added 4 ·5H 2 O is added by the volume ratio of 1:15-30 of water and ethanol, and adding SnF 2 Stirring at 50-70deg.C to dissolve thoroughly to obtain clear transparent sol solution, aging at room temperature, standing to gel, drying and pulverizing into powder, wherein the SnCl is prepared 4 ·5H 2 O and SnF 2 The molar ratio of (2) to (20): 1.
2. the preparation method according to claim 1, wherein the Mg (OH) is based on the mass of the tricobalt tetraoxide A or tricobalt tetraoxide B 2 The addition amount of (2) is 0.7% -1%, al 2 O 3 The addition amount of (C) is 0.8-1.5%, Y 2 O 3 The addition amount of the catalyst is 0.2% -0.5%, and the Co (OH) 2 The addition amount of (2) is 1.8% -3%.
3. The method of claim 1, wherein the speed of the blend is 500-800rpm for 20-40 minutes.
4. The preparation method according to claim 1, wherein the preparation of the monocrystal-like lithium cobaltate adopts gradient calcination, and the gradient calcination process specifically comprises the steps of preserving heat for 6-8 hours before 900-920 ℃, and then raising the temperature to 960-990 ℃ and preserving heat for 4-6 hours.
5. The method of claim 1, wherein the sintering process is sintering in an air kiln at 700-950 ℃ for 8-12 hours.
6. A lithium cobalt oxide positive electrode material, characterized by being produced by the production method according to any one of claims 1 to 5.
7. A lithium ion battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein an active material of the positive electrode contains the lithium cobaltate positive electrode material according to claim 6.
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CN110808373A (en) * 2019-09-24 2020-02-18 广东邦普循环科技有限公司 Single crystal lithium cobalt oxide and preparation method thereof and application of single crystal lithium cobalt oxide as lithium battery anode material
CN113247963A (en) * 2021-06-28 2021-08-13 湖南长远锂科股份有限公司 Preparation method of high-compaction high-rate high-voltage lithium cobalt oxide positive electrode material

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CN109786732A (en) * 2018-12-28 2019-05-21 广东邦普循环科技有限公司 Multimodal powder based on lithium transition-metal oxide and the application in rechargeable battery
CN109860544A (en) * 2018-12-29 2019-06-07 合肥融捷能源材料有限公司 A kind of high voltage lithium cobalt oxide anode and its preparation method and application
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